Teen's & dance school underwear rules under dance leotards

Many dance schools ask their students to not wear panties under their dance class leotards and costumes. But why do they ask this? And what do teenagers and adults then do when they are menstruating?

Is it ok for males to wear the girls standard ballet uniform to ballet class (leotard, tights, girls ballet shoes, etc.) because he wants to? This is assuming that the outfit has

The Importance of Dress Codes in a Dance Studio

Should my kid wear underpants, under their dance leotards and costumes?

Pack The Fourth Step to Surviving your kid's Dance or Ballet recital #shorts

Teens-and-underwear-FI

What Should I Wear Under a Sheer Dress? - The New York Times

3 Ways to Dress for a High School Dance (Girls) - wikiHow

Dress Code — Franklin School of Performing Arts

Girls & Ladies Dance Period Underwear ~ Dance Diva (Beige) ~ LeakSTOP Technology - Knicked Australia

These 9 Girls Were Kicked Out of School Dances for Their Outfits — Prom Disasters

The 50 Best Movie Dance Scenes of All Time

shorts Teen's & dance school underwear rules under dance leotards & costumes

How to Lay Out & Cut a Sewing Pattern for a Dance or Ballet Costume

How to Lay Out & Cut a Sewing Pattern for a Dance or Ballet Costume

Would these shorts (with no tights underneath) be appropriate for class? : r/BALLET